Connected: An Internet Encyclopedia
RFC 1812 - 4.3.1 INTRODUCTION

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### 4.3.1 INTRODUCTION

ICMP is an auxiliary protocol, which provides routing, diagnostic and error functionality for IP. It is described in [INTERNET:8]. A router MUST support ICMP.

ICMP messages are grouped in two classes that are discussed in the following sections:

ICMP error messages:

       Destination Unreachable     Section 4.3.3.1
       Redirect                    Section 4.3.3.2
       Source Quench               Section 4.3.3.3
       Time Exceeded               Section 4.3.3.4
       Parameter Problem           Section 4.3.3.5
       ICMP query messages:
       Echo                        Section 4.3.3.6
       Information                 Section 4.3.3.7
       Timestamp                   Section 4.3.3.8
       Address Mask                Section 4.3.3.9
       Router Discovery            Section 4.3.3.10

General ICMP requirements and discussion are in the next section.

Next: 4.3.2 GENERAL ISSUES

Connected: An Internet Encyclopedia
RFC 1812 - 4.3.1 INTRODUCTION